Field of the Invention
The present invention relates to a bracket apparatus for a composite spring, and, more particularly, to a bracket apparatus for a composite spring, configured for preventing a reduction in axial force of a U-bolt, which may occur due to contraction of a composite spring, in a rear-wheel two-axle suspension system having the composite spring.
Description of Related Art
A heavy-duty truck including a dump truck has two axles applied to the rear wheels thereof for traveling on an unpaved rough road so that the axles support the same load.
The rear-wheel suspension system of the heavy-duty truck having the two axles at the rear wheels thereof includes a pair of rubber springs that are respectively coupled to a rear-wheel-side front axle and a rear-wheel-side rear axle, and a spring member which is disposed in forward and rearward directions so that both end portions thereof are connected to the rubber springs.
A trunnion base having a trunnion shaft is positioned at the longitudinal middle portion of the spring member, and the trunnion base is assembled to a vehicle body frame. A U-bolt saddle (under saddle or lower saddle) is rotatably assembled to the trunnion shaft, and the U-bolt saddle and a spring bracket (upper saddle) are fixedly fastened together to the middle portion of the spring member with a U-bolt and a nut.
The spring member may be a multi-leaf spring including a steel material, or be a single composite spring including a glass fiber or a carbon fiber. The steel multi-leaf spring is advantageous in that it secures durability for the price, and the composite spring is advantageous in that it reduces weight and improves fuel efficiency.
Meanwhile, the composite spring has a characteristic that its volume largely varies depending on temperature, compared to the steel multi-leaf spring. In a low temperature of about −20° C. or less, the volume of the composite spring is significantly decreased as the contraction rate of the composite spring is increased.
Accordingly, in the rear-wheel two-axle suspension system that utilizes the steel U-bolt mixed with the glass fiber composite spring, when the volume (thickness) of the composite spring is decreased due to the contraction of the composite spring according to the change in atmospheric temperature, the axial force of the U-bolt may be reduced. For the present reason, peripheral suspension parts including the composite spring may be out of position and the durability thereof may be sharply deteriorated.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art which is already known to those skilled in the art.
The information included in the present Background of the Invention section is only for enhancement of understanding of the general background of the invention and may not be taken as an acknowledgment or any form of suggestion that the present information forms the prior art already known to a person skilled in the art.